WO2000031205A1

WO2000031205A1 - Container provided with a seal comprising a rubber and an aqueous fluid between a side wall and a top wall and/or bottom wall thereof and method for applying such a seal

Info

Publication number: WO2000031205A1
Application number: PCT/NL1999/000723
Authority: WO
Inventors: Frederik Maria Jacob Peet; Meindert Kramer
Original assignee: Koninklijke Emballage Industrie Van Leer N.V.
Priority date: 1998-11-25
Filing date: 1999-11-25
Publication date: 2000-06-02
Also published as: AU1417000A; NL1010652C2

Abstract

The invention relates to a container which is provided with a seal between a side wall and a top wall and/or bottom wall thereof, the seal comprising a rubber and an aqueous fluid, wherein the seal contains an electrolyte and the mass ratio of rubber:electrolyte in the seal is between 5:1 and 50:1. The invention also relates to a method for fitting a seal between a side wall of a container and a top wall and/or bottom wall thereof, wherein (a) the seal is applied by coagulation of an oil-in-water emulsion of an elastomer; and (b) the top wall and/or bottom wall is/are joined to the side wall of the container by folding over and wherein a layer, comprising an oil-in-water emulsion of an elastomer and a coagulant is simultaneoulsy applied to an edge of the top wall and/or bottom wall of the container.

Description

Container provided with a seal comprising a rubber and an aqueous fluid between a side wall and a top wall and/or bottom wall thereof and method for applying such a seal.

The present invention relates to a container which is provided with a seal between a side wall and a top wall and/or bottom wall thereof, the seal comprising a rubber and an aqueous fluid. The invention also relates to a method for applying a seal between a side wall of a container and a top wall and/or bottom wall thereof, wherein (a) the seal is applied by coagulation of an oil-in-water emulsion of an elastomer and (b) the top wall and/or bottom wall is joined to the side wall of the container by folding over. Examples of a container are a drum, a barrel or a tin can, that is to say containers which are suitable for packaging products such as chemicals and foodstuffs.

Such containers and such a method are known from the prior art. A conventional method for applying a seal comprises applying an oil-in-water emulsion of an elastomer to the edge of the top wall and/or bottom wall of the container. After applying the emulsion, the top wall and/or the bottom wall of the container is/are fed through a furnace to allow the elastomer to cure rapidly at high temperature to form a rubber. A disadvantage of this method is the laborious nature thereof, because a separate curing step is needed. Furthermore, an expensive furnace is needed.

It is also possible, after applying the emulsion, to cure the top wall and/or bottom wall in air to form a rubber. A disadvantage of this method is that curing takes at least a number of hours, which gives rise to logistics problems, in particular if products have to be packed in the containers within a short period.

Moreover, the side wall of the container and the top wall and/or bottom wall are folded over immediately after applying the emulsion. The container is subsequently fed through a furnace to stove the outer coating of the container. A disadvantage of this method is, in particular, that the temperature of the furnace, which is adjusted such that the outer coating is stoved, is sometimes too low to cure the elastomer to produce the rubber, with the result that inadequate curing of the elastomer takes place and a satisfactory seal is not obtained.

The present invention provides a solution to the problems described above and therefore relates to the container described above, wherein the seal contains an electrolyte and the mass ratio of rubbeπelectrolyte in the seal is between 5:1 and 50:1. Preferably the mass ratio of rubber: water in the seal is between 2:1 and 5:1.

The invention also relates to the method described above, wherein a layer comprising an oil-in-water emulsion of an elastomer and a coagulant are applied simultaneously to an edge of the top wall and/or the bottom wall of the container.

It will be obvious to those skilled in the art that, in principle, it would be possible, before or virtually simultaneously with folding over, to apply the coagulant to the top and/or bottom edge of the side wall of the container as well as, or instead of, to an edge of the top wall and/or the bottom wall of the container. However, according to the invention it is preferable that the coagulant is applied to the edge of the top wall and/or the bottom wall of the container.

An advantage of the method according to the present invention is that an expensive furnace is not required for applying the seal. A further advantage of the invention is that pre- coated, for example, pre-painted parts can be used for the production of the container. In this way good logistics planning is possible if large numbers of containers are needed for packing products within a short period.

Preferably the emulsion and the coagulant are applied by means of injection. The emulsion coagulates by means of the coagulant, that is to say the oil-in-water emulsion changes over to a water-in-oil emulsion, the viscosity of the emulsion increasing and, finally, the elastomer curing to give a rubber and an insoluble seal being provided, the water present in the emulsion separating off. The seal thus obtained is found to be exceptionally fluid-tight and gas-tight. Furthermore, in general it is necessary to apply the emulsion and the coagulant around the edge of the top wall and/or bottom wall of the container only once. However, it is customary to go round several times.

Pre-mixing of the two components .and then applying the mixture of these components will not be possible or will barely be possible in practice because the emulsion coagulates within a short time and the nozzle would rapidly become blocked. According to the invention the elastomer can be a natural rubber or a synthetic rubber.

An elastomer that is suitable according to the invention is Darex Drum 159V which is marketed by Darex UK Limited, Great Britain.

The emulsion preferably has a dynamic (Brookfield) viscosity of approximately 0.1 to approximately 100 Pas, in particular approximately 1 to approximately 50 Pas, and preferably contains a total percentage of solids of 50 % to 85 %, in particular of 60 % to 80 %.

The emulsion can contain fillers such as talc or silicon dioxide. In this case the rubber obtained by coagulation of the elastomer will also contain these fillers and the ratios and quantities specified in this description are then calculated on the basis of the total mass of the rubber and the fillers.

The coagulant is preferably a solution of an electrolyte, in particular a solution of a salt and/or an acid in water. The electrolyte can be any electrolyte that causes emulsions to coagulate and preferably has an acid action. Of course, the solution can contain more than one electrolyte. Examples of suitable electrolytes are acetic acid, formic acid, citric acid and the salts thereof, sodium sulphate, aluminium sulphate, sodium hydrogen sulphate, ammonium sulphate, zinc chloride and the hydrates thereof. Good results can in particular be obtained with the abovementioned acids. The disadvantage of the acids is that these substances can give rise to corrosion. This can be prevented by using a coagulant which also has a buffer action in addition to an acid action. According to the invention the coagulant is therefore preferably an electrolyte having an acid and a buffer action.

The ratio of the emulsion to the coagulant is approximately 4:1 to 25: 1, preferably 6:1 to 20:1.

If the container has not passed through a furnace, the mass ratio of rubbeπwater, calculated on the b.asis of the total quantity of rubber and any fillers present, will be between

2:1 and 5:1 and the mass ratio of rubbeπcoagulant, calculated on the basis of the total quantity of rubber and any fillers present, will be between 5:1 and 50:1 in the seal of the container.

If the container provided with the seal has passed through a furnace, the quantity of water in the seal will, depending on the furnace temperature used, be lower than the abovementioned ranges, but the mass ratio of elastomer/coagulant will remain approximately the same.

According to the present invention the side wall, the top wall and/or the bottom wall of the container can be covered on the inside and/or outside, for example with a coating. With known methods two to three furnaces must be used. One or two furnaces are needed for stoving the outer coating and/or inner coating and one for making the emulsion coagulate. However, furnaces are expensive equipment and such a method also requires a great deal of energy, so that such a method has the disadvantage that it is associated with high costs. In contr.ast, according to the method according to the invention one fewer furnace is needed, specifically that for making the emulsion coagulate. A further advantage of the method according to the invention is that the parts of the container are optionally coated before the seal is applied.

According to the present invention the container can be dispatched immediately to the destination after applying the seal and joining the top wall and/or bottom wall to the side wall of the container, without passing through a furnace. As can be seen from the above description, this is a great advantage, in particular if products have to be packed in containers within a short period. Furthermore, the seal of rubber and liquid/electrolyte is found to have exceptional fluid- and gas-tightness, especially if the folded joint of the container is subjected to slight deformation by impacts.

The invention will now be explained on the basis of an example.

Example

The following combination of components is applied to the edge of the top wall and of the bottom wall by means of injection: 10 gram Darex Drum Compound 159V and 1 gram of a 50 % solution of Al₂(SO₄)₃.18H₂O in water. The top wall and the bottom wall are then joined to the side wall of the container by folding over. The container is found to meet all specifications imposed, without the container having passed through a furnace:

1. After sawing open the folding over the emulsion is found to have coagulated to form insoluble rubber and water in a mass ratio of approximately 2.9:1 and a rubber: electrolyte ratio of approximately 30:1.

2. The container is exceptionally leak-tight and sufficiently pressure-resistant and the container passes the drop test at the required drop heights.

The technical data of Darex Drum Compound 159V are as follows:

(a) colour: red;

(b) total solids: 80 - 82 %;

(c) Dynamic (Brookfield) viscosity: 8500 - 9500 cP RVF (= 8.5 - 9.5 Pas).

Claims

1. Container which is provided with a seal between a side wall and a top wall and/or bottom wall thereof, the seal comprising a rubber and an aqueous fluid, wherein the seal comprises an electrolyte and the mass ratio of rubber: electrolyte in the seal is between 5:1 and 50:1.

2. Container according to Claim 1 , wherein the mass ratio of rubber:water in the seal is between 2 : 1 and 5:1.

3. Method for applying a seal between a side wall of a container and a top wall and/or bottom wall thereof, wherein:

(a) the seal is applied by coagulation of an oil-in-water emulsion of an elastomer; and

(b) the top wall and/or bottom wall is joined to the side wall of the container by folding over, wherein: a layer comprising an oil-in-water emulsion of an elastomer and a coagulant is applied simultaneously to an edge of the top wall and/or bottom wall of the container.

4. Method according to Claim 3, wherein the emulsion and the coagulant are applied by means of injection.

5. Method according to Claim 3 or 4, wherein the elastomer is a natural or a synthetic rubber.

6. Method according to one of Claims 3 - 5, wherein the emulsion has a viscosity of 0.1 to 100 Pas.

7. Method according to one of Claims 3 - 6, wherein the coagulant is a solution of an electrolyte.

8. Method according to one of Claims 3 - 7, wherein the coagulant is a solution of an electrolyte having .an acid and a buffer action.

9. Method according to one of Claims 3 - 8, wherein the ratio of the emulsion to the coagulant is between 4: 1 and 25: 1.

10. Method according to one of Claims 3 - 9, wherein the side wall, the top wall and/or the bottom wall of the container are coated.

1 1. Method according to one of Claims 3 - 10, wherein after applying the seal and joining the top wall and/or bottom wall to the side wall of the container the latter is despatched immediately to the destination without passing through a furnace.

12. Container obtainable according to the method according to one of Claims 3 - 11.

AMENDED CLAIMS

[received by the International Bureau on 14 April 2000 (14 04.00); original claim 1 amended; remaining claims unchanged (1 page)]

1. Container which is provided with a seal between a side wall and a top wall and/or bottom wall thereof, the seal comprising a rubber and an aqueous fluid, wherein the seal comprises an electrolyte and the mass ratio of rubbeπelectrolyte in the seal is between 5: 1 and

50:1, and wherein the mass ratio of rubber: water in the seal is between 2: 1 and 5: 1. calculated on the basis of the total quantity of rubber and any filters present.

STATEMENT UNDER ARTICLE 19 (1)

EP A 194 796 discloses a method for making a rubbery mass by forming a fluid mass wherein the use of an oven to dry said fluid mass is not necessary. The fluid mass comprises an aqueous dispersion of at least 50 parts calcium sulphate hemihydrate per 100 parts of a visco elastic polymer.